Malignancy Risk for Fine-Needle Aspiration of Thyroid Lesions According to The Bethesda System for Reporting Thyroid Cytopathology

Fine-needle aspiration (FNA) is an important test for triaging patients with thyroid nodules. The 2007 National Cancer Institute Thyroid Fine-Needle Aspiration State-of-the-Science Conference helped instigate the recent publication of The Bethesda System for Reporting Thyroid Cytopathology. We reviewed 3,080 thyroid FNA samples and recorded interpretations according to the proposed standardized 6-tier nomenclature, and pursued follow-up cytology and histology. Of the 3,080 FNAs, 18.6% were nondiagnostic, 59.0% were benign, 3.4% were atypical follicular lesion of undetermined significance (AFLUS), 9.7% were "suspicious" for follicular neoplasm (SFN), 2.3% were suspicious for malignancy (SM), and 7.0% were malignant. Of 574 cases originally interpreted as nondiagnostic, 47.9% remained nondiagnostic. In 892 cases, there was follow-up histology. Rates of malignancy were as follows: nondiagnostic, 8.9%; benign, 1.1%; AFLUS, 17% (9/53); SFN, 25.4%; SM, 70% (39/56), and malignant, 98.1%. Thus, classification of thyroid FNA samples at the University of Virginia Health System, Charlottesville, according to The Bethesda System yields similar results for risk of malignancy as reported by others. Universal application of the new standardized nomenclature may improve interlaboratory agreement and lead to more consistent management approaches.